Electric-lighting system.



E. & N. R. BOOTH. ELECTRIC LIGHTING SYSTEM.

APPLICATION FILED OCT. 26, 1910.

Patented Apr. 30, 1912.

I V D D I l I I) EDGAR BOOTI-IAND NORMAN RUSSELL BOOTH, OF HALIFAX, ENGLAND.

ELECTRIC-LIGHTING SYSTEM.

Specification of Letters Patent.

Patented Apr. 30, 1912.

Application filed October 26, 1910. Serial No. 589,254.

To all whom it may concern:

Be it known that we, EDGAR BOOTH and NORMAN RUSSELL BOOTH, subjects of His Majesty the King of Great Britain, residing at Halifax, in the county of York, England, have invented a new and useful Improvement in Electric-Lighting Systems, of which the following is a specification.

It has been proposed to arrange electric incandescent lamps connected in series in such manner that when a lamp of the series becomes inoperative the circuit is automatically completed through a shunt circuit to such lamp thereby maintaining the flow of current to the remaining lamps in the series. This has been effected by interposing in some part of such shunt circuits metal pieces which are'separated by insulating material which will withstand the electro-motive force thereat when the lamps are in a nor mal Operation but which on an increase of elect-ro-motive force thereat owing to a lamp becoming inoperative will be destroyed and then contact will be made between the metal pieces so as to conduct the current through the shunt circuit and the remaining lamps of the series are maintained in operation. Now in an arrangement of this kind all that has hitherto been relied upon to break down or destroy the insulating material in the shunt circuit is the above referred to increase of electro-motive force in such circuit consequent upon a lamp of the series becoming inoperative and in practice it has been found to be very diflicult to so arrange the metal pieces and the insulating material separating them that in every case this rise of electro-motive force shall be suflicient-ly great to break down or destroy the insulating material and thus establish the shunt circuit, so that this arrangement has been unreliable in O oration. It has also been proposed to pro uce a rise of potential sufficient to insure the breaking down of the insulation by placing the lamps in series with the secondary circuit of an induction coil the primary coil of which is arranged to be momentarily traversed by a current from the mains upon the failure of a lamp.

According to the present invention a single circuit self-induction coil is employed and the necessary rise of potential is produced by the extra current induced by the instantaneous and complete interruption automatically or otherwise of a circuit shunting the lamps and in which the self induct-ion coil is included as hereinafter explained with reference to the accompanying drawings.

The improvements comprising the present invention are illustrated by way of example in the accompanying drawing, in which Figure 1 is a diagrammatical representation of a system of installation: and Fig. 2 is also a diagrammatical representation of a modified arrangement.

Referring particularly to the drawings, Fig. 1 illustrates four incandescent lamps (1 arranged in series in the usual manner across the mains g and h each lamp having a shunt circuit d containing metal pieces 7v k which are prevented from coming into metallic contact by the insulating material 121 which preferably consists of a piece of paper. is a shunt wire across the mains g and 72. containing a. resistance 7' and a switch 3 by means of which the shunt circuit 0 may be broken or interrupted. It is essential for the successful breaking down of the insulating body m that the break in the shunt circuit should be as instantaneous as possible. and a simple and efiicient way of doing this is to break such circuit at two or more points simultaneously. In Fig. 1, the switch 8 is shown to break simultaneously at two points viz :at t and e. n is an electromagnet and is common to'both the circuit comprising the lamps a in series and the shunt circuit 0. lVhen the lamps a are in a normal operation the switch 8 is open and consequently the shunt circuit (F is not completed. On the series circuit being interr-upted by reason of one of the lamps a becoming inoperative, the shunt circuit 0 is completed and broken by closing and opening the switch 8 and as the electro-magnet n is also c ontained in this circuit, on breaking it the extra current above referred to is produced. The efi'ect of breaking this shunt circuit at two or more points simultaneously is to prevent the extra current from areing across the points of interrupt-ion and to force it to pierce and break down the insulating i naterial mseparating the metal pieces 70 70 thereby allowing them to come into contact and thereby reestablishing metallic continuity in the circuit comprising the lamps in series. It will be readily understood that the shunt circuits d may in clude a body 7* the resistance of which is approximately equal to the resistance of the filament to which it forms a shunt but such resistance should preferably be a non-inductire resistance. The function of these resistances 1" one-of which is thrown into the circuit when insulating pieces k are broken down is to choke the current so that no in jurious impulses can injure the lamps which are still lighted.

By means of the above described arrangement metallic continuity in the series circuit may be immediately reestablished on a lamp becoming inoperative by operating the switch .9 as above described, but it has the disadvantage that it is not automatic and all the lamps in the series are liable to be extinguished until the switch 8 is so operated. The following arrangement obviates this latter disadvantage and automatically reestablishes continuity in the series circuit upon a lamp becoming inoperative.

Referring to Fig. 2, this again illustrates four incandescent lamps a arranged inseries across the mains g and h each lamp as before having a shunt circuit at containing metal pieces 7a 7a separated by insulating material m, and resistance 1". c is the shunt circuit across the mains g and h containing the resistance r, and n is the electro-magnet common to both the circuit comprising the lamps a in series and the shunt circuit 0. f is an iron armature attached to 'a spring Z and to which latter is also attached the contact piece j. The normal position of the contact piece j by reason of the spring Z is in contact with and bridging the terminals 2 and c.

The manner of operation is as follows On supplying current to the mains g and h if there is continuity in the series circuit, as the electro-magnet n is contained in such circuit, the armature f is attracted to it and the shunt circuit 0 is broken simultaneously at t and L'. Let it now be assumed that the filament of one of the lamps a breaks. The series circuit being thereby interrupted the armature f is released and the contact piece j again comes into contact with and bridges the terminals t and t. This establishes the shunt circuit 0 and as the electro-magnet 'n is also contained in this shunt circuit it is again excited and the armature f is attracted. This has the desired effect of breaking the shunt circuit at two points simultanemlsly viz:at t and w, the extra current is produced and as hereinbefore described breaks down the insulating material in the circuit which forms a shunt to the lamp the filament of which has broken. Metallic continuity in the series circuit having been reestablished the armature f remains attracted to the magnet a by the current flowing through the series circuit and the shunt circuit 0 remains broken.

The thickness of the insulating material and of the pieces of metal separated thereby are shown increased in both the figures in order to better illustrate them.

We claim 1. In a system of series incandescent elec tric lighting, a main circuit a plurality of incandescent lamps arranged in series in said circuit, each lamp having a shunt circuit from said main circuit, a pair of adjacently arranged metal pieces in each shunt circuit, insulating material arranged between said metal pieces, a shunt wire across said main circuit, means for opening and closing the circuit including said shunt wire, an electromagnet included in said main circuit and in the circuit including said shunt wire, said circuit including said shunt wire being normally open whereby when said circuit is closed and again opened the extra current induced from said electro-magnet breaks down the said insulation material and permits current to flow through one of said first-named shunt circuits.

2. In a system of series incandescent electric lighting, a main circuit, a plurality of incandescent lamps arranged in series in said circuit, each lamp having a shunt circuit from said main circuit, a pair of'adjaeently arranged metal pieces in each shunt circuit, insulating material arranged between said metal pieces, a shunt wire across said main circuit, a switch arranged on said shunt wire, an electro-magnet included in said main circuit and the circuit including said shunt wire, and means operated by said electro-magnet for opening and closing the circuit including said shunt wire.

In testimony whereof we aflix our signatures in presence of two witnesses.

EDGAR BOOTH. NORMAN RUSSELL BOOTH.

\Vitnesses:

AUGUSTUS E. INGRAM, W ALTER BROUGHTON. 

